Publication details

Type Inference for First-Class Messages with Feature Constraints

Martin Müller, Susumu Nishimura

International Journal of Foundations of Computer Science 11(1):29-63, 2000

We present a constraint system, OF, of feature trees that is appropriate to specify and implement type inference for first-class
messages. OF extends traditional systems of feature constraints by a
selection constraint , ``by first-class feature
tree'' , which is in contrast to the standard selection
constraint . We
investigate the satisfiability problem of OF and show that it can be
solved in polynomial time, and even in quadratic time if the number
of features is bounded. We compare OF with Treinen's system EF of
feature constraints with first-class features, which has an
NP-complete satisfiability problem. This comparison yields that the
satisfiability problem for OF with negation is NP-hard. We even
obtain NP-completeness, for a specific subclass of OF with negation
that is useful for a related type inference problem. Based
on OF we give a simple account of type inference for first-class
messages in the spirit of Nishimura's recent proposal, and we show
that it has polynomial time complexity: We also highlight an
immediate extension of this type system that is desirable but makes
type inference NP-complete.